The concentration of caffeine in an energy soft drink was determined by standard addition using a...
The concentration of caffeine in an energy soft drink was determined by standard addition using a n emission spectrofluorimeter. The following procedure was used: a standard caffeine solution was prepared by adding 0.6482g of caffeine to 100 cm3 of water.
A series of solutions were prepared by adding known volumes of the standard solution to the soft drink before diluting to 100 cm3. The volume of standard and the caffeine peak area are shown in the table
|
Energy Drink (cm3) |
Vol of caffeine Std added (cm3) |
Final volume (cm3) |
Emission |
|
|
10 |
0 |
100 |
23450 |
|
|
10 |
5 |
100 |
33335 |
|
|
10 |
10 |
100 |
43220 |
|
|
10 |
15 |
100 |
53105 |
|
|
10 |
20 |
100 |
62990 |
Determine the concentration of caffeine in the soft drink as mg cm-3.
A.
21.8
B.
7.7
C.
12.3
D.
1.2
Homework Answers
By the addition of each 5ml of standard into energy drink, the floursence intensity is raised around 10000 units.
So, here standard made by dissolving 0.6482g in 100cm3
So, 5cm3 standard contains = 0.03241g of caffeine.
So, emission intensity 10000 -------> 0.03241g
23450 -------> ? g
Amount of caffeine = 0.076g = 76mg
Sample volume 10cm3, so 10cm3 contains 76mg.
Then in 1cm3 contains = 7.6mg/cm3
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